Amyloidosis is not a single disease entity but rather a diverse group of progressive disease processes characterized by extracellular tissue deposits of a waxy, starch-like protein called amyloid, which accumulates in one or more organs or body systems. As the amyloid deposits accumulate, they begin to interfere with the normal function of the organ or body system. There are at least 15 different types of amyloidosis. The major forms are primary amyloidosis without known antecedent, secondary amyloidosis following some other condition, and hereditary amyloidosis.
Many diseases of aging are based on or associated with amyloid-like proteins and are characterized, in part, by the buildup of extracellular deposits of amyloid or amyloid-like material that contribute to the pathogenesis, as well as the progression of the disease. These diseases include, but are not limited to, neurological disorders such as Alzheimer's Disease (AD), Lewy body dementia, Down's syndrome, hereditary cerebral hemorrhage with amyloidosis (Dutch type); the Guam Parkinson-Dementia complex. Other diseases which are based on or associated with amyloid-like proteins are progressive supranuclear palsy, multiple sclerosis, Creutzfeld Jacob disease, Parkinson's disease, HIV-related dementia, ALS (amyotropic lateral sclerosis), Adult Onset Diabetes, senile cardiac amyloidosis, endocrine tumors, and others, including macular degeneration.
The polypeptide β-amyloid (Aβ) is likely to play a central role in the pathogenesis of Alzheimer's disease (AD). Vassar et al., J. Neurosci. 29:12787-12794 (2009). Aβ polypeptide accumulation in the CNS results in synaptic dysfunction, axon degeneration and neuronal death. The brains of AD patients show a characteristic pathology of prominent neuropathologic lesions, such as neurofibrillary tangles (NFTs), and amyloid-rich senile plaques. The major component of amyloid plaques is Aβ. These lesions are associated with massive loss of populations of central nervous system (CNS) neurons and their progression accompanies the clinical dementia associated with AD.
Aβ is the proteolytic product of the precursor protein, beta amyloid precursor protein (β-APP or APP). APP is a type-I trans-membrane protein which is sequentially cleaved by two proteases, a β- and γ-secretase. The β-secretase, known as β-site amyloid precursor protein cleaving enzyme 1 (BACE1), first cleaves APP to expose the N-terminus of Aβ, thereby producing a membrane bound fragment known as C99. Vassar et al., J. Neurosci., 29:12787-12794 (2009) and UniProtKB/Swiss-Prot Entry P56817 (BACE1_HUMAN). The γ-secretase then is able to cleave C99 to produce the mature Aβ polypeptide. Aβ is produced with heterogenous C termini ranging in length from 38 amino acids to 43 amino acids. The 42 amino acid form of Aβ (Aβ42) is the fibrillogenic form of Aβ and is over produced in patients with Down's syndrome and has been suggested to play a role in the early pathogenesis of AD. Vassar et al., J. Neurosci. 29:12787-12794 (2009). BACE1 has thus become a therapeutic target as its inhibition would presumably inhibit APP and Aβ production.
Indeed, BACE1 knock-out mice (BACE1−/−) do not produce cerebral Aβ, confirming that BACE1 is the major, if not only, enzyme responsible for producing Aβ in the brain. Roberds et al., Human Mol. Genetics. 10:1317-1324 (2001). Moreover, BACE1 knockout mice in AD models do not form amyloid plaques; cognitive defects and cholinergic dysfunction are rescued as well. McConlogue et al., J. Biol. Chem. 282: 26326-26334 (2007); Ohno et al., Neuron 41: 27-33 (2004); and Laird et al., J. Neurosci. 25:11693-11709 (2005). Additionally, BACE1 heterozygous knock-out mice have reduced plaque formation indicating the complete inhibition of BACE1 activity is not necessary for plaque reduction. McConlogue et al., J. Biol. Chem. 282: 26326-26334 (2007).
Recently, APP has been shown to be a ligand for Death Receptor 6 (DR6) which triggers caspase-dependent neuronal cell body death and axon pruning Nikolaev et al., Nature 457: 981-989 (2009). In addition, a BACE1 compound inhibitor impaired degeneration of axons and cell bodies. Id. These results point to a model in which APP, via DR6 binding may contribute to AD.
It would be beneficial to have an effective therapeutic inhibitor of BACE1 to reduce APP and Aβ production in patients with neurological diseases and disorders, such as AD. The invention provided herein relates to such inhibitors, including their use in a variety of methods.
All references cited herein, including patent applications and publications, are incorporated by reference in their entirety.